Explore the vast range of titles available.

This paper summarizes two sessions of the workshop during the XIX meeting of the European Association for Haematopathology (EAHP) held in Edinburgh in September 2018 dedicated to lymphomas of the gastrointestinal tract. The first session focused on the clinical and pathological features of primary gastrointestinal T cell and NK-cell lymphoproliferative disorders. The distinction between precursor lesions (RCD type 2) and enteropathy-associated T cell lymphoma were stressed, including the discussion of new diagnostic markers for the identification of aberrant phenotypes. Indolent T cell lymphoproliferative disorders of the gastrointestinal tract cases showed phenotypic heterogeneity with novel molecular alterations in few cases, such as STAT3-JAK2 fusion. In addition, novel clonal markers of disease, such as AXL and JAK3 somatic variants support the neoplastic nature of NK-cell enteropathy. The session on gastrointestinal tract B cell lymphoproliferations was dedicated to B cell lymphoproliferative disorders that arise primarily in the gastrointestinal tract (i.e., duodenal-type follicular lymphoma) or preferentially involve the digestive tract, such as large B cell lymphoma with IRF4 translocation and mantle cell lymphoma (MCL), including diverse molecular subtypes (i.e., CCND3-positive MCL mimicking MALT lymphoma). Challenging cases of high-grade B cell lymphomas with complex genetic profiles demonstrated the usefulness of novel molecular diagnostic methods such as targeted NGS to identify high-risk genetic features with potential clinical impact.

Double-hit lymphoma (DHL) is a subgroup of aggressive lymphomas with both MYC and BCL2 gene rearrangements, characterised by a rapidly progressing clinical course that is refractory to aggressive treatment and short survival. Over time, the definition was modified and now includes diffuse large B-cell lymphoma (DLBCL) with MYC translocation combined with an additional translocation involving BCL2 or BCL6. Some cases that have a similar clinical course with concomitant overexpression of MYC or BCL2 proteins were recently characterised as immunohistochemical double-hit lymphomas (ie, double-protein-expression lymphomas [DPLs]). The clinical course of these DPLs is worse than so-called standard DLBCL but suggested by some studies to be slightly better than DHL, although there is overlap between the two categories. Present treatment does not allow cure or long-term survival in patients with genetic or immunohistochemical double-hit lymphomas, but several new drugs are being developed.

Netrin‐1 and B‐cell maturation antigen (BCMA) are currently being evaluated as therapeutic targets in oncology. However, studies investigating their expression in mature human lymphoid malignancies are sparse. This study aimed to investigate the expression of BCMA and Netrin‐1 in a large cohort of lymphomas to determine their potential role as biomarkers or therapeutic targets. BCMA and Netrin‐1 expression was investigated comprehensively using immunohistochemistry in a cohort that included 261 B‐cell lymphomas, 45 T‐cell lymphomas, and 55 classical Hodgkin lymphomas. Netrin‐1 displayed a cytoplasmic staining pattern in plasmablastic lymphomas (27/28, 96%) and classical Hodgkin lymphomas (8/55, 15%). BCMA displayed cytoplasmic staining in most plasmablastic lymphomas (17/20, 85%). Among mature B‐cell lymphomas, Netrin‐1 and BCMA displayed sensitive (96% and 85%, respectively) and specific (100% and 95%, respectively) staining in plasmablastic lymphomas. These results suggest that these proteins may help pathologists in complex diagnoses and reinforce the interest in developing clinical trials assessing Netrin‐1 or BCMA‐targeted therapies in plasmablastic lymphoma and classical Hodgkin lymphomas, for which our therapeutic arsenal is weak.

Most adult B cell lymphomas originate from germinal center (GC) B cells, but it is unclear to what extent B cells in overt lymphoma retain the functional dynamics of GC B cells or are blocked at a particular stage of the GC reaction. Here we used integrative single-cell analysis of phenotype, gene expression and variable-region sequence of the immunoglobulin heavy-chain locus to track the characteristic human GC B cell program in follicular lymphoma B cells. By modeling the cyclic continuum of GC B cell transitional states, we identified characteristic patterns of synchronously expressed gene clusters. GC-specific gene-expression synchrony was lost in single lymphoma B cells. However, distinct follicular lymphoma–specific cell states co-existed within single patient biopsies. Our data show that lymphoma B cells are not blocked in a GC B cell state but might adopt new dynamic modes of functional diversity, which opens the possibility of novel definitions of lymphoma identity. Human follicular lymphomas arise from germinal center B cells. Milpied and colleagues use single-cell transcriptomic analysis to show that follicular lymphoma cells lose synchronized gene-expression patterns that characterize normal germinal center B cells.

Almost one‐third of all splenic marginal zone lymphoma (SMZL) cases express B‐cell receptor immunoglobulin (BcR IG) encoded by the IGHV1‐2*04 gene, implicating antigen selection in disease ontogeny. Evidence supporting this notion mostly derives from low‐throughput sequencing approaches, which have limitations in capturing the full complexity of the BcR IG gene repertoire. This hinders the comprehensive assessment of the subclonal architecture of SMZL as shaped by antigen selection. To address this, we conducted a high‐throughput immunogenetic investigation of SMZL aimed at the comprehensive characterization of the somatic hypermutation (SHM) and intraclonal diversification within the IG genes. We identified significant differences in the SHM and ID profiles between cases expressing the IGHV1‐2*04 gene and those expressing other IGHV genes. Specifically, IGHV1‐2*04 cases displayed (i) targeted SHM resulting in recurrent replacement SHMs, and (ii) significantly more pronounced intraclonal diversification, reflecting ongoing antigen selection. Overall, our findings suggest that SMZL cases expressing the IGHV1‐2*04 gene have a distinct immunogenetic signature shaped by microenvironmental pressure on the clonotypic BcR IG, corroborating the idea that this group may represent a distinct molecular variant of SMZL.

Patients with follicular lymphoma have heterogeneous outcomes. Predictor models to distinguish, at diagnosis, between patients at high and low risk of progression are needed. The objective of this study was to use gene-expression profiling data to build and validate a predictive model of outcome for patients treated in the rituximab era. A training set of fresh-frozen tumour biopsies was prospectively obtained from 160 untreated patients with high-tumour-burden follicular lymphoma enrolled in the phase 3 randomised PRIMA trial, in which rituximab maintenance was evaluated after rituximab plus chemotherapy induction (median follow-up 6·6 years [IQR 6·0–7·0]). RNA of sufficient quality was obtained for 149 of 160 cases, and Affymetrix U133 Plus 2.0 microarrays were used for gene-expression profiling. We did a multivariate Cox regression analysis to identify genes with expression levels associated with progression-free survival independently of maintenance treatment in a subgroup of 134 randomised patients. Expression levels from 95 curated genes were then determined by digital expression profiling (NanoString technology) in 53 formalin-fixed paraffin-embedded samples of the training set to compare the technical reproducibility of expression levels for each gene between technologies. Genes with high correlation (>0·75) were included in an L2-penalised Cox model adjusted on rituximab maintenance to build a predictive score for progression-free survival. The model was validated using NanoString technology to digitally quantify gene expression in 488 formalin-fixed, paraffin-embedded samples from three independent international patient cohorts from the PRIMA trial (n=178; distinct from the training cohort), the University of Iowa/Mayo Clinic Lymphoma SPORE project (n=201), and the Barcelona Hospital Clinic (n=109). All tissue samples consisted of pretreatment diagnostic biopsies and were confirmed as follicular lymphoma grade 1–3a. The patients were all treated with regimens containing rituximab and chemotherapy, possibly followed by either rituximab maintenance or ibritumomab–tiuxetan consolidation. We determined an optimum threshold on the score to predict patients at low risk and high risk of progression. The model, including the multigene score and the threshold, was initially evaluated in the three validation cohorts separately. The sensitivity and specificity of the score for the prediction of the risk of lymphoma progression at 2 years were assessed on the combined validation cohorts. In the training cohort, the expression levels of 395 genes were associated with a risk of progression. 23 genes reflecting both B-cell biology and tumour microenvironment with correlation coefficients greater than 0·75 between the two technologies and sample types were retained to build a predictive model that identified a population at an increased risk of progression (p<0·0001). In a multivariate Cox model for progression-free survival adjusted on rituximab maintenance treatment and Follicular Lymphoma International Prognostic Index 1 (FLIPI-1) score, this predictor independently predicted progression (adjusted hazard ratio [aHR] of the high-risk group compared with the low-risk group 3·68, 95% CI 2·19–6·17 [p<0·0001]). The 5-year progression-free survival was 26% (95% CI 16–43) in the high-risk group and 73% (64–83) in the low-risk group. The predictor performances were confirmed in each of the individual validation cohorts (aHR comparing high-risk to low-risk groups 2·57 [95% CI 1·65–4·01] in cohort 1; 2·12 [1·32–3·39] in cohort 2; and 2·11 [1·01–4·41] in cohort 3). In the combined validation cohort, the median progression-free survival was 3·1 years (95% CI 2·4–4·8) in the high-risk group and 10·8 years (10·1–not reached) in the low-risk group (p<0·0001). The risk of lymphoma progression at 2 years was 38% (95% CI 29–46) in the high-risk group and 19% (15–24) in the low-risk group. In a multivariate analysis, the score predicted progression-free survival independently of anti-CD20 maintenance treatment and of the FLIPI score (aHR for the combined cohort 2·30, 95% CI 1·72–3·07). We developed and validated a robust 23-gene expression-based predictor of progression-free survival that is applicable to routinely available formalin-fixed, paraffin-embedded tumour biopsies from patients with follicular lymphoma at time of diagnosis. Applying this score could allow individualised therapy for patients according to their risk category. Roche, SIRIC Lyric, LYSARC, National Institutes of Health, the Henry J Predolin Foundation, and the Spanish Plan Nacional de Investigacion.

Background Intravascular large B‐cell lymphoma (lVLBCL) is a very rare type of large B‐cell lymphoma. Methods We conducted a retrospective study on IVLBCL patients treated from 2000 to 2016 in LYSA cooperative group centers. Results Sixty‐five patients were identified in 23 centers. Median age at diagnosis was 69 years (range 23–92). Thirty‐four patients (64%) had an IPI score >3 and 40 patients (67%) had a performance status ≥2. The most frequent extra‐nodal locations were bone marrow (n = 34; 52%), central nervous system (n = 25; 39%), and skin (n = 21; 33%). Nodal involvement and endocrine system were observed in 34% (n = 22) and 18% (n = 12) of all cases, respectively. Twenty‐six patients (41%) had macrophage activation syndrome. Tumor cells were frequently CD5 positive (52%) with a non‐germinal center origin (86%). BCL2 was expressed in 87% of all samples analyzed (n = 20) and 43% of patients had a MYC/BCL2 double expression. Fifty‐six patients were treated with a regimen of chemotherapy containing rituximab, among whom 73% reached complete remission. The median progression‐free survival (PFS) and median overall survival (OS) were 29.4 months and 63.8 months, respectively. History of autoimmune disorder (Hazard ratio [HR] 3.3 [1.4–7.8]; p < 0.01), nodal involvement (HR 2.6 [1.4–5.1]; p < 0.01), lack of anthracycline (HR 0.1 [0–0.4] for use; p < 0.001), or no intensification at first‐line regimen (p = 0.02) were associated with worse PFS. High‐dose methotrexate use was not associated with better PFS or OS. Conclusions Our study highlights the aggressive clinical picture of IVLBCL, in particular the frequency of macrophage activation syndrome, and the need for new therapies despite a response to R‐CHOP‐like regimen similar to non‐intravascular diffuse large B‐cell lymphomas. Intravascular large B‐cell lymphomas in a large cohort present aggressive features and a dismal prognosis is suggested when associated with autoimmune disorders and nodal involvement.

Session 2 of the 2018 European Association of Hematopathology/Society for Hematopathology Workshop focused on lymphomas arising in immune-privileged sites: both lymphomas arising in the traditionally described “immune sanctuary” sites of the central nervous system (CNS) and testes, as well as those arising at sites of local immune privilege. Primary CNS large B cell lymphoma and primary testicular large B cell lymphoma were discussed, and the biology of these unique tumors was highlighted by several cases showing the classic mutation profile including MYD88 L265P and CD79B. The tendency of these tumors to involve both the CNS and testis was also reinforced by several cases. Four cases of low-grade B cell lymphomas (LGBCL) of the CNS were discussed. Two were classic Bing-Neel syndrome associated with LPL, and two were LGBCL with plasmacytic differentiation and amyloid deposition without systemic disease. Rare examples of systemic T and NK cell lymphomas involving the CNS were also discussed. Several cases of breast implant–associated anaplastic large cell lymphoma (BI-ALCL) were submitted showing the typical clinicopathologic features. These cases were discussed along with a case with analogous features arising in a patient with a gastric band implant, as well as large B cell lymphomas arising alongside foreign materials. Finally, large B cell lymphomas arising in effusions or localized sites of chronic inflammation (fibrin-associated diffuse large B cell lymphoma [DLBCL] and DLBCL associated with chronic inflammation) were described. The pathogenesis of all of these lymphomas is believed to be related to decreased immune surveillance, either innate to the physiology of the organ or acquired at a local site.

Crystal‐storing histiocytosis and Bing‐Neel syndrome are two diseases induced by paraproteins. Herein, we report a rare case of crystal‐storing histiocytosis associated with Bing‐Neel‐like neurological manifestations in the context of a small B‐cell lymphoma with plasmacytic differentiation, presumed to be a marginal zone lymphoma. This case shows the need to search for a B lymphoproliferative disorder after a crystal‐storing histiocytosis diagnosis and to hypothesize that a B‐lymphoproliferative disorder other than Waldenström macroglobulinemia can induce Bing‐Neel syndrome.